<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>模拟 router</title>
</head>
<body>
  <ul>
    <li><a href="#/">turn yellow</a></li>
    <li><a href="#/blue">turn blue</a></li>
    <li><a href="#/green">turn green</a></li>
  </ul>
  <script>
    window.onload = function () {
      class Routers {
        constructor () {
          this.routes = {}
          this.currentUrl = ''
          this.refresh = this.refresh.bind(this)
          window.addEventListener('load', this.refresh, false)
          window.addEventListener('hashchange', this.refresh, false)
        }
        route (path, callback) {
          this.routes[path] = callback || function () {}
        }
        refresh () {
          this.currentUrl = location.hash.slice(1) || '/'
          this.routes[this.currentUrl]()  //  执行回调函数
        }
      }
      window.Router = new Routers()
      let content = document.querySelector('body')
      function changeBgColor (color) {
        content.style.backgroundColor = color
      }
      Router.route('/', function () {
        changeBgColor('yellow')
      })
      Router.route('/blue', function () {
        changeBgColor('blue')
      })
      Router.route('/green', function () {
        changeBgColor('green')
      })
    }
  </script>
</body>
</html>
